New Study Shows Physical Changes Happen to Create the ‘Mom Brain’

Recognizing a new mother's ability to be more empathetic and intuitive is something that most accept based on pure observation, and experience. Now, a new study actually gives a scientific glimpse into the physical changes that happen to mothers, and why.

My fellow mothers will recognize the symptoms of so-called “mom brain”—that feeling of fuzzy forgetfulness that seems to strike many moms as we juggle diapers and dirty dishes. But does this condition have any basis in science?

A new study in Nature Neuroscience suggests the answer is yes. Pregnancy does seem to change a woman's brain—perhaps permanently—so that she can better connect with other people.

Prior research has suggested the pregnant brain may have fuzzy moments—but they don't last long. For example, memory function does decline, especially when it comes to verbal information, during the last trimester. But after the baby is born, mom's memory and cognitive ability seem to bounce back. In fact, some studieshave found motherhood actually makes rodents smarter.

The new study, by a team of researchers based in Spain, gathered four groups of participants: 25 first-time mothers, both before and after the birth; 20 women who had not yet had children; 19 first-time fathers; and 17 men without children.

These participants were scanned in an fMRI machine so that researchers could compare their brain structures. The changes they saw were mainly associated with gray matter, the brain tissue that contains neurons and synapses involved with memory, emotions, and decision-making, among other functions.

The result? Pregnant women lost a significant amount of gray matter, in a pattern similar to what happens during puberty—another time when women experience a surge of sex hormones like estrogen. This adolescent “synaptic pruning” doesn't mean we get dumber as teens. Instead, the brain is simply becoming more efficient and refined, in a process associated with healthy cognitive and emotional development. In other words, the teen brain is “leveling up” into greater maturity as it sheds gray matter it no longer needs.

Could something similar be happening with women when they go through pregnancy? When the researchers scanned the brains of the same women two years later, the changes remained in place, suggesting they may be permanent. There were no similar changes in the brains of first-time fathers or childless men and women. In fact, note the authors, the pattern was so distinctive that it could be used to tell whether a woman had ever given birth.

The biggest changes were concentrated in the cerebral cortex, which—among its many functions—plays a key role in processing relationships with other people. The areas that showed pruning were specifically related to the “theory of mind” network—that is, the part of the brain that tries to figure out what people are thinking and feeling. The researchers speculate that this may enhance mothers' ability to accurately guess their infant's emotional states and meet their needs.

To test their theory, the researchers showed the women in the study photos of their own babies while administering an fMRI. Indeed, the parts of the brain affected by the gray matter changes were also the areas that lit up the most in response to pictures of the mothers' own babies (when compared to photos of other people's infants).

In addition, the researchers found that the change in gray matter “significantly” predicted the quality of mother-to-infant attachment, as assessed through a survey. The more gray matter lost, the more positive the mothers felt about interactions with their baby.

In other words, the changes that unfold in a pregnant woman's brain almost certainly indicate that she's growing as a person—especially when it comes to figuring out what other people need and feel.

So, new moms, don't feel too bad about “mom brain.” You may be forgetful at times, but you're primed to forge a stronger bond with your baby.